Technical Abstract:
The discovery that broccoli (Brassica oleracea L., Italica Group) seedling sprouts contain high levels of glucoraphanin has stimulated much interest in seed production by this crop. Glucoraphanin is the precursor of sulforaphane, an isothiocyanate that may provide chemoprotection against certain carcinogens when consumed in broccoli heads or sprouts. Previously, we found that selected, self-compatible inbreds (conventional and doubled haploid) of broccoli will produce significant yields of uniform seed. In the present study, we measured the glucoraphanin concentrations of seed produced from those same inbreds grown in two greenhouse and two outdoor screen cage environments. Our objective was to determine if seed glucoraphanin concentrations of different inbreds was consistent across environments. Seed glucoraphanin content was measured by a hydrophilic interaction liquid chromatography method employing an HPLC. In all environments, seed glucoraphanin concentrations varied significantly among inbreds. Overall, concentration for a given inbred was relatively similar across all four environments. One doubled haploid had the highest mean seed glucoraphanin concentration at 70.4 umole/gdw across all environments, and a conventional inbred from an open-pollinated population had the next highest at 61.9 umole/gdw. Two doubled haploids had mean seed glucoraphanin concentrations less than 10 umole/gdw across all environments, while the remaining inbreds were intermediate. Results indicate that observed genetic variation was more important than the environmental variation in determining glucoraphanin concentration in broccoli seed produced in these trials. It appears that development of self-compatible inbreds that combine consistent high yield and high glucoraphanin should be readily accomplished though inbreeding and selection.